1. Field of the Invention
This invention relates to a light diffusion preventing structure, and more particularly to a light diffusion preventing structure used in conducting light from a light source into a enclosed space that is defined by a structure having an interior finished with a structural member, while the light source is located outside of the enclosed space.
2. Description of the Related Art
FIG. 3 depicts a relation between a light source and a conventional structure provided with a hole for allowing the light to pass from the light source through structure. FIG. 4 shows a spatial relationship between a grille used as a conventional structure and a light source for providing a spotlight on a shift lever or gear lever.
In FIGS. 3 and 4, a lamp 20 comprises an incandescent lamp or other light source fitted into a lamp holder 21. The grille 22 is an ornamental panel attached as a part of the interior trim of a vehicle. The grille 22 also includes a hole 23 for allowing the light from lamp 20 to spotlight a shift lever 30.
In the conventional structure, the light from lamp 20 spotlights the shift lever 30 with light having an irradiation angle xcex8. The direction of the spotlight illumination is determined by the relationship between the light source 20 and the opening that is located at a lower surface and defined by a lower edge of the hole 23 of the grille 22.
However, the light of the lamp 20 irradiates a first thickness surface 23a or an inner peripheral surface of the hole 23 at one side of the grille 22 as well as a second thickness surface 23b or an inner peripheral surface of the hole 22 at the other side of the grille 22. The brightness at the first thickness surface 23a and the second thickness surface 23b is inversely proportional to square of the distance from the lamp 20 to the surfaces 23a, 23b. The surfaces 23a, 23b are located near the lamp 20. Moreover, the first thickness surface 23a is a surface facing the light source or the lamp 20, while the second thickness surface 23b is a surface more parallel to a radiating direction of the light. Consequently, the first thickness surface 23a has an increased brightness when compared with the second thickness surface 23b. As a result, the first thickness surface 23a tends to be brighter than its surroundings. If such light is located at a position in which light from first thickness surface 23a shines directly into the eyes of a driver at a position where the light from the first thickness surface 23a can be reflected by an inside rear view mirror into the eyes of the driver, it may cause the driver to be distracted.
An object of the present invention is to provide a light diffusion preventing structure by which the light passing through a hole is not diffused by the sidewalls of the hole.
According to a first aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member. The structural member has a hole that passes a light from the light source. The hole has a three-dimensional shape that has a first opening located near the light source and a second opening located away from the light source. Further, the area of the first opening is smaller than the area of the second opening. Indeed, the circumferential edge of the second opening is located completely outside of a zone defined between imaginary straight lines connecting the point light source and the circumferential edge of the first opening provided that the light source is the point light source. This configuration ensures that the imaginary straight lines never touch any of the inner peripheral surface of the structural member between the first and second opening.
According to a second aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member. The structural member has a hole that allows light from the light source to pass through the member and into an interior space. The hole has a three-dimensional shape that includes a first opening located near the light source and a second opening located away from the light source. The first and second openings are configured so that the area of the first opening is smaller than an area of the second opening. Imaginary straight lines connecting the circumferential edge of the first opening and the opposite circumferential edge of the second opening have a crossing angle of not more than 160 degrees and more preferably not more than 150 degrees.
According to a third aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member.
The structural member has a hole that allows light from the light source to pass through the member and into an interior space. The hole has a three-dimensional shape that includes a first opening located near the light source and a second opening located away from the light source. The first and second openings are configured so that the area of the first opening is smaller than an area of the second opening. The holes are also configured so that the circumferential edge of the second opening is located outside a zone defined between first imaginary straight lines connecting a point light source and the circumferential edge of the first opening provided that the light source is the point light source. The first imaginary straight lines are never touch any of the inner peripheral surface of the structural member between the first and second opening. Second imaginary straight lines connecting the circumferential edge of the first opening and the opposite circumferential edge of the second opening have a crossing angle of not more than 160 degrees and more preferably not more than 150 degrees.
Further objects and advantages of the invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the invention are clearly shown.